Automatic work guidance mechanisms



March 12, 1963 J. E. CLEMENS ETAL AUTOMATIC WORK GUIDANCE MECHANISMS 9Sheets-Sheet 1 Filed March 9, 1961 In ven fora 1757a: ECZemens RayWHczrruff Ben E. *JEhnszone 'iZ5D7u36Z) 2c y Mark .D. 15060 iike .HbraGe WWeeks .351 t/zez rflfiormgl March 12, 1953 J. E. CLEMENS ETAL 3,080,836

AUTOMATIC WORK GUIDANCE MECHANISMS Filed March 9, 1961 9 Sheets-Sheet 2March 12, 1963 Filed March 9, 1961 in VI 1 sTzEmNq J. E. CLEMENS ETALAUTOMATIC WORK GUIDANCE MECHANISMS 9 Sheets-Sheet 3 March 12, 1963 J. E.CLEMENS ETAL 3,080,836

AUTOMATIC WORK GUIDANCE MECHANISMS Filed March 9, 1961 9 Sheets-Sheet 4Mardl 1963 J. E. CLEMENS ETAL 3,030,836

AUTOMATIC WORK GUIDANCE MECHANISMS Filed March 9, 1961 9 Sheets-Sheet 5March 12, 1963 J. E. CLEMENS ETAL 3,080,836

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ST'OP NEEDLE P March 1963 J. E. CLEMENS ETAL 3,080,836

AUTOMATIC WORK GUIDANCE MECHANISMS 9 Sheets-Sheet 7 Filed March 9, 1961.5 Z: wurmjait NHBOAP u m h FE: wmflhsuiwuu L March 1963 J. E. CLEMENSETAL 3,030,835

AUTOMATIC WORK GUIDANCE MECHANISMS Filed March 9, 1961 9 Sheets-Sheet 9\\\\\\III///// Z United State Patent? 3,080,836 AUTOMATIC WORK GUIDANCEMECHANISMS John E. Clemens and Ray W. Hermit, Xenia, Ben B.

Johnstone, Dayton, James 1). Ray, Wilmington, Mark D.Sobottke,'Kettering, and Horace'W. Weeks, Dayton, Ohio, assign'ors toUnited Shoe MachincryCorporation, .Flemington, NJ, a corporation of NewJersey Filed Mar. 9, 1961, Ser. :No. 94,556 26 Claims. .(Cl; 112-457)lected course, for instance substantially parallel to prescribedcurvature such as that of an edge of the material even though this edgebe of changing curvature. .Although the invention as herein illustratedis embodied in a sewing machine wherein the reciprocable tool is in theform of a needle for securing a binding strip in parallel edge relationto a shoe part, it will be understood that in its various aspects theinvention is :not thus limited either as to materials employed, thenature of the function performed, is. a securing or sewing operation, orto the particular machine which is shown merely by way of example, itbeing .rccognized that the invention has utility in a wide variety ofmachines which may employ different types of tools.

Hand controlled steeringof Work pieces in a machine becomes tedious andinaccurate when they are irregular in shape and non-rigid, and the pathof operation of a tool thereon must, at least in part, be other thanrectilinear. Also, the production capability of a machine in which suchwork pieces are being manually fed is likely 'to be somewhat reduced, ithas been observed, when the operating path of the tool involves a sharpor reverse 'curve and engagements of the tool with the work tend tointerrupt its feeding movement. Accordingly, efforts have been made toprovide guidance mechanism which, unlike the more cumbersome controlmeans developed in the machine tool industry for orthogonally movingwork-carrying tables, is adapted automatically to steer sheet materialby action taken directly on the work itself. One approach, for instance,is that disclosed in an application for United States LettersPatentSerial No. 827,970, filed July 17, 1959, in the names of Hans F.Schaefer, Jr.,

and Robert K. Jenner, Jr, now Patent No. 2,979,745, and

another is disclosed in an applicationSerial No. 27,214, filed May 5,1960, in the names of William S. 'Iouchman and Loyd A. Barnes, nowPatent No. 3,034,781. The

former, relating to anedge folding machine, is briefly distinguished inthat its work guidance is effected by a pair of spaced members exertingtorque for automatically swinging the work about only one turning centerlocated substantially at or near its edge, whereas in the latter case,exemplified in a skiving machine, the work steering means may cause theinstantaneous center of turning to be shifted along a known line. Workguidance as ali'orded by these developments and for their range ofapplication has been found to relieve the burden on an operator Whilefacilitating production of his machine.

In the light of the foregoing it is a general object of this inventionto provide, in a machine including a tool for operating at successivelocalities on a work piece, improved means operative at only a singlework engaging locality for automatically and intermittently guiding thework piece with respect to the tool to cause its operating path toextend along a preselected course, for example,

ice

2 inparallelrelation to'theedge of the work. Another and considerablymore-specific object of this invention is to provide a machine forautomatically and progressively securing as by means of a seam, in-edgeto edge relation, the-upper of a shoe and a .piece or strip such as anedge binding. ln accordance with these objects and as illustratedherein, a feature of this invention resides in the combination, inamaehine having a reeiproeable work e-n-' gaging tool and :mechanism forfeeding the work inthe intervals when the tool is disengaged, of"independent means automatically effectivebetween said feeding intervals,predetermin'edly to steerthe work by turning it about its locality ofengagement with the tool, thesteerin'g means being responsive -toselected curvature such as that of the periphery of the work just aheadof the tool. While the tool may, for instance, be an actuated punch,fastener inserter, embosser or marking 'tool, or other instrument ofmovable type for physically operating on the work, it will be apreciated "that the'term tool" as herein used is intended also "tocomprehend non-moving eleiifeirt's ar- 'r-anged'to engage the Wb'ik'tb'trea't-it, examples or such elements being a cement applyin nozzle, 2burnishin member or the like. In the illustrated machine the esemplary"tool, as "above stated, is a reciproc'able needle,

and hence the work steering means of this invention preferably operatesolely while the needle is penetrating "a work piece toe'xert forces forbodilyfpivotirig the latter only about the needle in its successive workengaging localities. Advantageously, the work steering means is adapted'to be installed in a sewing or other machine of otherwise conventionalconstruction, the illustrated post sewing machine incorporating a commonform of orbital dog feeding mechanism for advancing the workinstepby-step translation in the intervals when the needle is withdrawnfrom the work. In partial resemblance to'the above-mentioned Schaefe'ret a1. disclosure, the present steering means includes aservo-controlled reversible, variable speed steering wheel, thepresentnovel construction, however, in a simple and unique manner,avoiding any necessity for providing a mechanism for this wheel whichmust differentially allow for the transl'at-ory feed speed as effectedby the feed dog and its cooperative presser foot. 7

A further feature of the invention consists in the provision, in amachine having an operating tool and feed means cyclically operative toadvance the work by in- 'crements, of improved automatic work steeringmeans including only a single steering wheel and a presser member whichis arranged to be moved into and out of cooperative Work engagingposition inwardly of the feed means from the tool, the mounting of thesteering means being such that its operation is responsive to that ofthe feed means and automatically effected alternately therewith.Advantageously, this construction permits a servo motor controllingvelocity of the wheel to operate with zero error during straight linefeeding of the 'work in translation. As herein shown the feed presserfoot prefer ably is a roll carried by a usual vertical, downwardlyurged, presser post, and the steering presser member is preferably aroll carried by a lever pivotally connected to the presser post andspring-urged into operative position. Thus, advantageously, the steeringwheel may be continuously driven regardless of the relative position ofthe steering presser roll, this position being determined by that of thefeed presser roll, and the controlling servo motor being continuouslyresponsive to changes in selected governing curvature such as edgecurvature of the work at a locality immediately ahead of the operatingzone of the needle.

The above and other features of the invention, including means forautomatically changing incremental teed 3 n or stitch length withoutinterrupting operation of the machine, and means for sensing a selectedwork corner automatically to effect stopping of the machine or simplydiscontinued steering but continued feeding (for instance as a new workpiece is being introduced to the machine),

together with other novel combinations and arrangements of parts willnow be more particularly described in connection with an illustrativemachine and with reference to the accompanying drawings thereof, inwhich:

FIG. 1 is a view in front elevation of a post type sewing machine, atrest, for securing binding strips to articles such as shoe uppers and inwhich this invention is embodied;

'FIG. 2 is a view in front elevation, partly in section, showing on alarger scale and in operating condition the sewing machine head and posttogether with automatic work guidance means including :a steering wheeland cooperative steering presser roll;

FIG. 3 is a. view in side elevation of mechanism shown in FIG. 2;

FIG. 4 is a view in front elevation showing operating instrumentalitiesincluding a needle as indicated in FIG. 2, on a further enlarged scale,portions being in section to illustrate actuating means for the steeringpresser roll;

FIG. 5 is a section taken on the line VV of FIG. 3 indicating themountings of a feed presser roll and the steering presser roll;

FIG. 6 is a plan view of the work supporting post indicating therelative positions of the work steering wheel and a throat plateassembly accommodating the sewing needle, a feed dog, and control cellswith reference to an adjustable null line and work piece;

FIG. 7 is a section taken on the line VII-VII of FIG. 6 extendingthrough a needle hole;

FIG. 8 is a graph comparing the torque required to turn a given leatherwork piece in the machine with the torque available from the steeringwheel in a cycle of operations;

FIG. 9 is a view in front elevation, with a portion broken away, of theright hand side of the machine and showing stitch length changemechanism;

FIG. 10 is a detail of an axial part in the stitch length changemechanism;

FIG. 11 is a section, on a larger scale, taken on the line XI-XI of FIG.9;

FIG. 12 diagrammatically indicates a work piece portion having an edgeof inside curvature at which stitch length, merely because of suchcurvature, normally is increased;

FIG. 13 shows the sa-me edge as shown in FIG. 12 but with stitch lengthreduced actually to provide more uniformity in stitch length appearanceand an increased number of stitches at the curvature;

FIG. 14 is an end elevation, partly in section, illustrating means forautomatically stopping the machine with its needle in up position, theparts being shown in position when the machine is stopped;

FIG. 15 is an end elevation corresponding with the upper portion of FIG.14;

FIG. 16 is a section taken on the line XVI-XVI of FIG. 14;

FIG. 17 is a block diagram of the work guidance system and associatedelectric machine controls;

FIG. 18 is an electrical diagram of power amplification andpreamplification units as connected between the guidance cell and aservo motor;

FIG. 19 is an electrical diagram complemental to that of FIG. 18 andshowing motor and bias supply controls; and

FIG. 20 is an alternate form of steering presser foot as mounted forcooperation with the steering wheel of this machine.

General Organization In many respects, unless otherwise noted herein,the sewing machine illustrative of the invention is of a commerciallyavailable construction and conveniently adaptable to receive automaticwork guidance means as will be described. It comprises a hollow frame 22(FIGS. 1-3) secured on a bench 24 and having a vertically r..-ciprocable needle 26 (FIGS. 1-4). In guiding the work in the machine bythe exercise of this invention and without operator attendance once thework has been presented. the operating path of the needle on the workmay be caused, as will be explained, to extend in any selected course.For purposes of illustration a work piece, such as an upper U (FIGS. 1and 6) of a shoe, is automatically guided with respect to the needle 26to cause the stitches of a seam to extend parallel to a work piece edgethus securing an article such as a binding strip S (FIGS. 1 and 3) inparallel edge relation. The needle is disposed to be received in aneedle hole 23 (FIG. 6) of a bobbin cover or throat plate 31 screwedonto the upper end of a composite machine post 32 (FIGS. 1-3 and 6)upstanding from the bench 24. As usual for operating the needle theframe 22 supports in bearings a horizontal main shaft 34 (FIGS. 3 and 9)operat-ively coupled to a needle post 36 (FIGS. 1-5) verticallyreciprocable in a bore formed in an overhanging head 38 of the frame 22.The main shaft 34 and an orbitally actuated feed dog 40 (FIGS. 3, 4 and6) are driven from a main DC. motor 42 (FIGS. 1, 9, 17 and 19) throughmechanism subsequently described.

It will be understood that the feed dog 40 intermittently rises abovethe level of the supporting surface of the throat plate 39 to feed thework step-by-step in translation past the needle in the intervals whenthe latter is disengaged from the work, the direction of feed being fromright to left in FIG. 3 or from bottom to top as viewed in FIG. 6. Forcooperating with the feed dog a feed presser roll 44 (FIGS. 2, 4 and 5)is carried by an end of an arm 46, the other end of which is secured toa bracket 48. This bracket is fixedly mounted by means of a setscrew 50(FIG. 5) on the lower end of a presser foot post 52 (FIGS. 3, 4 and 5arranged for movement in a vertical bore formed in the head 38. In usualmanner the feed presser roll 44 is yieldingly urged toward workengagingposition when the post 52 is in its lower position. a spring 54 (FIG. 3)having its lower end bearing on a bracket 56 afiixed to the post and anupper end abutting a sleeve 58 adjustably threaded in the head 38. Ahand lever 60 (FIG. 3) pivoted to the head at 62 has an end surface 64disposed to engage a horizontally projecting portion of the bracket 56as the lever is turned clockwise as viewed in FIG. 3 for the purpose ofraising the post and the feed presser roll 44 from the work. Asindicated in FIG. 3 by dotted lines the surface 64, when horizontal,latches the post 52 in its upper and inoperative position. Work-engagingpressure of the roll 44 may be modified by suitably turning the sleeve58, some slight pressure normally being desirable for a given thicknessof the work even while the dog 40 is in lowered position and disengagedfrom the work, though this pressure should not be enough to affect workguidance by means hereinafter explained.

A reel 66 (FIG. 1) for holding a supply of the binding strip S to besewn to the shoe upper U (FIG. 6) is rotatably mounted in a holder 68removably secured to the machine head. The strip extends downwardlythrough a guideway 70 (FIG. 1, 3 and 5) formed on the front end of abracket 72 secured to the presser post bracket 48, the exit end of theguideway being disposed somewhat ahead of the needle hole 28 andlaterally spaced to aline an edge of the strip with a peripheral edge ofthe upper in the locality about to be stitched, both edges then beingclose to, if not exactly in, tangency with a null line L (FIGS. 5 and 6)determined by automatic guidance means next to be explained.

Automatic Work Guidance System in an upright wall 86 (FIGS. 2 and 3)Within the machine post .32 and hasan upper portion of its toothedperiphery projecting through a slot 88 (FIG. 6) of the post forfrictional engagement with the underside of the upper U. As best showninFIG. 6 the wheel 80 is thus arranged to engage the work at a localityspaced farther inwardly of the work from the needle operating zone thanis the feed dog 49, the work engaging localities of the needle, dog, andsteering wheel lying substantially in a line normal to the null line L.For operating the wheel 80 a bracket 90 (FIGS. 2 and 3) secured to theunderside of the top of the bench 24 mounts a housing 92 for suitablereduction gearing (not shown) having output shafts 94, 96 which areuniversally coupled. Accordingly, the servo motor 84 together with itsstabilizing tachometer generator 98 (FIGS. 17, 18) is mounted on thehousing 92 reversibly to drive the shaft 96 and a bevel gear 100 on theupper end thereof which meshes with a bevel gear 102 formed coaxially onthe steering wheel 80.

The curvature sensing means above referred to for continuously governingspeed and direction of the servo controlled steering wheel 80 is, inthis case, arranged to sense curvature of the edge of the upper itselfat a locality "just ahead of that about to be acted upon by the needle26. The means comprises electrical circuitry including a light sensitivedevice in the form of a work sensing or guidance solar cell 1% (FIGS. 6,l7 and 18) embedded in the throat plate Bil, a DC. bias supply unitgenerally designated 110 (FIGS. 17 and 19), a preamplifier unitgenerally designated 112 (FIGS. 17 and 18), and a power amplifier unitgenerally designated 114. Location of the cell 1% is critical to servomotor stability and important to derive accurate steering or errorsignals. Preferably the cell is spaced within a range of fromsubstantially zero to five feed increments ahead of the needle hole 28,the best location usually being within about one feed increment andhence closely adjacent to the operating path of the needle 26. Also,considered transversely of the null line L, the cell 103 is disposed sothat, when the operating locality of the upper is correctly orientedwith respect to the needle, about one-half of the cell is covered by the\VOIli piece acting as a shutter, and the other half of the cell 1638 isexposed to light beams directed from a source above, such as a bulb 116(FIGS. 1, 2 and 4) mounted on the bracket 48 or, if preferred, simplydependent from the head 38. By reason of change in curvature of the workpiece edge at a point closely adjacent to the operating locality as theupper is fed past the needle, the cell 1138 is more or less covered bythe upper U. Accordingly, a DC. voltage from the curvature detectingcell, generated when the cell is covered exactly to the null line L bythe upper, is directed to one leg of a resistance circuit within thepreamplifier unit 112 and nulled by application of a DC. voltage, equalin magnitude and polarity, from the bias supply 11% to a second leg ofthe resistance circuit, a third leg of this circuit including a variableresistor 118 (FIG. 18) having a manual control 120 (FIG. 1) for fineadjustment of the null point or line L as desired. The electrical nulland consequently the null line L are established by the fact thatvoltages equal in magnitude and polarity are present in the tworesistance circuits in the preamplifier 112 and that theelectromechanical chopper unit of the preamplifier 112 alternately readsthe voltage present in the two resistance circuits. Theelectromechanical chopper unit of the preamplifier 112 directs thesevoltages to .a coupling capacitor 121 (FIG. 18) of the preamplifier 112which filters the chopper ripple signal, which is undesirableparticularly at the servomotor null point, to give only a systemreference voltage and therefore .no neter-ror signal. Each increment offeed is therefore likely to change the voltage present in the resistancecircuit connected to the cell 168 and thereby createsa net voltagediiference as seen by the capacitor 121 constituting an error signal.The servomotor 84 is dependent upon error signal voltage phasing fordirection of rotation information. This informationis supplied by virtueof the vfact that the net voltage difference producing the error signalmust .be larger than the system reference voltage and that thisdifierence may alternately appear at the elecvtromechanical choppercontact, connected to bias supply resistance circuit, or the contactconnected to the cell 108 resistance circuit, as the cell 108 is eithercovered more or uncovered more. This signal, which is now an .A.C.signal by virtue of the electromechanical chopper, is amplified and ispassed through a contact K1C1 (FIG. 18), when closed, to a functionalcontrol box generall designated .122 (FIGS. 1, 17 and 19). The contactK101 is closed by actuation of a foot switch 124 (FIGS. 1, 1.7 and 19)to energize a relay coil K1 shown in FIG. 19 and, in fact, mounted onthe chassis for the preamplifier 112. After appropriate switching in thefunctional control box 122 the error signal is fed tothe power amplifierunit 114 and ultimately to the servo motor 84 itself. As will beunderstood by those experienced in servo control art, the so-called pureerror thus derived is modified in known manner for damping purposes byemploying the tachometer generator '98 to add a rate of change of errorsignal, the addition being effected by a variable resistor and asummingresistor in the preamplifier unit 112. Also, in known manner,other components of the preamplifier unit enable the servo motor 84 toachieve maximum power by insuring the voltages in its control andreference winding are in quadrature.

As has been indicated, while the steering wheel 80 is continuouslyoperative and hence always potentially able to exert a steering torqueon the work, it desirably is actually elfective toguide or steer thework only when the needle 26 has penetrated, in this case, the upper andstrip S and can thus serve as the pivot or instantaneous center ofturning about which the work is bodily swung by the wheel. For thuscausing the steering to be effected alternately with each increment offeeding, and synchronously with successive work engagements of theneedle, mechanism next to be explained is provided for automaticallycausing the steering presser roll 82 to be urged into an effectivetorque exerting position of greater cooperative work engaging pressureand then retracted to a substantially ineffective position wherein itswork engaging pressure is minimal permitting slippage of the wheel 80and substantially no effective guidance torque. Experiments have shownthat the wheel 80 will 'slip on most upper leather, for instance, whenthe guidance torque is reduced to about 10 inch-ounces or less (see FIG.8). The roll 82 is carried on the front end of a lever (FIGS. 3 to 5inclusive) pivotally secured by a fulcrum pin 132 to the bracket 48. Therear end of the lever 130 is connected by means of a tension spring 134to the lower end of a stud 136 adjustably threaded heightwise in atubular support 138 secured to the machine head 39. A knurled head 14%of the stud 136 may be rotated suitably to modify the clamping pressure(and consequently the torque level before slippage) exerted by thesteering presser roll 82 according to the severity of curvaturesinvolved in the operating path of the needle and with regard to thecharacter of the material to be guided. A collar 142' (FIG. 4) pinned onthe stud 136 aids in guiding it heightwise in the support 138 which isvertically slotted at .144

. as shown in FIGS. 1 and 2 to accommodate the lever 130.

feeding is emphasized because it economically enables the guidancesystem, after each feeding increment, bodily to turn the work to thecorrect degree about the work engaging needle and until the full errorsignal is nulled or reduced to zero; hence upon upward retraction of theneedle the thread of the stitch next to be inserted following thefeeding increment will lie in accurately parallel relation to the workedges. It will be understood that when the feed dog 40, acting throughthe work, lifts the feed presser roll 44 in the course of a feedingincrement, the steering torque available from the wheel 80 is reducedsubstantially as shown in FIG. 8 since resultant raising of the presserfoot post 52 and of the fulcrum pin 132 relieves the upward forceexerted by the spring 134 and hence correspondingly reduces thework-engaging pressure of the steering presser roll 82 to allowineffectual rotation of the wheel 80. Consequently the required servoresponse frequency is not equal to the incremental feeding frequency ofthe feed dog 40 but is only a function of the equivalent frequency asgenerated by the radius of curvature and the average peripheral speed ofthe work. Thus, the required servo response frequency may be many timesless than the incremental feeding frequency. Considered further withreference to FIG. 8, when the feed dog 40 is being lowered at the end ofa feeding increment, the wheel 80, by reason of the now increasing workclamping pressure exerted by the spring 134 through the steering presserroll 82, is ready and able to exert a steering torque theoreticallylimited only by the output of the servo motor 84.

Machine Drive Mechanism In addition to the automatic work guidancesystem described, the illustrative machine includes in highlyadvantageous combination therewith and as parts of its drive mechanismnext to be considered means generally designated 148 (FIGS. 9-11 and 15)for changing stitch length, particularly in the course of traversingsharper inside curvatures such as shown in FIGS. 12 and 13, withoutinterrupting operation of the machine, and a device generally designated150 (FIGS. 9, 14 and 16) for autornatically stopping the machine withits operating tool, the needle 26, in up or inoperative position. Firstwith regard to the means 148, the main shaft 34 is hollow to receive aconically ended portion 152 (FIGS. and 11) of an axially slidableoperating shaft 154 (FIGS. 1, 9 and 11). The latter as indicated inFIGS. 14 and 16 extends axially through a hand wheel 156 keyed on theshaft 34, and through parts of the device 150 comprising a earn 158rotatable on a reduced hub of the hand wheel, a pulley 161) to which thecam 158 is keyed, a cam plate 162 straddling the cam, and a guide plate164 having opposed, parallel walls 166, 166 for radially guiding the camplate 162 as displaced by the cam 158. The guide plate 164 is bored toreceive a pair of pins 168, 168 (FIG. 16) for securing the plate 164 tothe hand wheel. A pulley 170 (FIG. 9) on the drive shaft of the motor 42is fitted with an endless belt 172 for transmitting power to the pulley160. For changing stitch length at the will of the operator, he shiftsthe shaft 154 to the right as viewed in FIG. 9 by any suitable means, aknee pad 174 (FIGS. 1 and 9) being provided in this case for thispurpose. Thus actuation of the pad to turn its carrying lever 176counterclockwise as viewed in FIG. 9 about a fulcrum 178 provided by abracket 180 secured to the bench operates linkage including an arm 182of a lever 184, and a link 186 connecting the arm 182 to the lower endof a long vertical lever 188. The upper end of this lever 18$ is pivotedto a bracket 19% (FIGS. 1, 9 and secured on the main frame, and isconnected by trunnion pins 192, 192 to a collar 194 afiixed on the shaft.154. This shifting of the shaft 154 is elfected against resistance of areturn spring 1% connecting the bench and the lever 184.

Referring mainly to FIGS. 9 and 11, actuation of the pad 174 axially toshift the conical portion 152 as just described causes this portion tobear on the rounded end of a plug 193 adjustably threaded into anenlarged hub portion 266 of an eccentric 202, the plug extendingradially through a bore formed in the wall of the main shaft 34.Accordingly, the hub portion 2%, which is mounted on a pivot pin 204projecting from a flange of a collar 265 secured on the shaft 34, isurged counterclockwise as viewed in FIG. 11 by means of a spring pressedplunger 2518 hearing on the shaft 34 at a locality diametrically opposedto the plug 198. The eccentric 202 is therefore shifted to a position ofgreater concentricity with the shaft 34 to the limit adjustablypermitted by a short stitch adjusting setscrew 210. For this purpose thescrew 210 extends into one end of an arcuate slot 212 (FIG. 11) formedin the hub portion 202 for endwise engagement with a stop screw 214threaded through the flange of the collar 266 at a localitydiametrically opposite to the pivot pin 204. The displacement to lesseneccentricity of the eccentric 262, it will be understood, is effectiveto shorten the stitches by reason of shortening the throw of aconnecting rod 216 (FIGS. 3 and 9) for rocking a customary sewingmachine feed shaft 218 (FIG. 3) horizontally mounted in the bench 24. Asusual a crank 229 secured on the shaft 218 causes a lever 222 (FIG. 3)to impart feeding movements in translation to the dog 40, its heightwisemovements being concurrently imparted by a rotary cam 224 working in aforked arm 226 of the lever 222.

FIG. 11 depicts the screws 210, 214 in their operating positions, forinstance before negotiating the curvature indicated in FIG. 13, wherethe stitches have been shortened and hence adjustably increased innumber. Without means to change to shorter stitch length at sharperinside curvatures it is found that their length is, in fact, otherwiselengthened as shown in FIG. 12 thereby producing unsightly, nonuniformappearance in the product. Shorter stitch length at such curvatureyields better construction and a binding of better appearance, forinstance, when the strip S is later folded over. Re lease of the pad 174permits the spring 196 to restore the normal stitch length withoutinterrupting operation of the machine, the stop screw 214 then abuttinga long stitch adjusting screw 228 (FIG. 11) threaded through the portion292 and into the opposite end of the slot 212.

Coming now more especially to the device for stopping the machine inneedle-up position, it is essential for decreasing the operating time ofa machine cycle and permits the work always to be correctly located inthe machine before commencing automatic operation. The device is adaptedto terminate rotation of the main sha t 34 in a position correspondingto that in which it has raised and retracted the needle 26 from thework. A motor control unit generally designated 230 (FIGS. 1, 17 and 19)includes a variac 232 (FIG. 19) for changing AC. voltage applied to arectifying bridge 234 which, in turn, provides a DC. voltage to themotor 42 as selected by means of a knob 236 (FIG. 1) for thuscontrolling variable speed of the motor. The latter is energized foroperation at the preselected speed by the actuation of the foot switch124 to energize relays K2 and K5 (FIG. 19), resultant AC. voltage beingapplied to a rectifier bridge 238 through a contact KSAI and directed asDC). voltage through contacts K2A1 and K2A2 to the motor. Cutting off ofthe motor drive voltage by means of the device 159 as now explainedstops the shaft 34 in the desired position. Upon release or opening ofthe foot switch 124 the relays K1, K2 and K5 are deenergized, and arelatively low AC. voltage is accordingly applied to the rectifierbridge 238 through a now closed contact KSBI (FIG. 19). This gives riseto a DO. reversing voltage being applied to the motor 42 throughnow-closed contacts K251 and K2B2. Accordingly, when the machine hasstopped and its main shaft 34 starts to reverse (i.e. turns in theclockwise direction indicated in PEG. 14), the camplate 162 is outwardlydisplaced radially until its projection 24% (FIG. 14) depresses astriker 242 rpivotally carried by a lever 244 itself pivotally securedon a pin 245 in a bracket 246 which is afiixed to the right-hand end ofthe machine frame 22. The arrangement is such that a projection 248(FIGS. 9 and 14) on the lever 24d consequently opens a switch 250 (FIGS.9, 14 and 19) removing all motor drive voltage immediately to stop themachine in needle-up position. Better to understand this operation ofthe device it is pointed out that the earn 158 is formed with a rise2'52 extending over an arc of 60. During forward or sewing operation ofthe shaft 34 (counterclockwise rotation as viewed in FIG. 14), thetorque required from the cam 158 reacts against an internal wall 254 ofthe cam plate 162 causing it to retract inwardly in the guide plate 164with the switch operating protection 240, the latter then beingineifectual while pivoting the projection 24% clockwise (as viewed inFIG. 14) against resistance of a spring 255 which normally holds thestriker against a stop 257 formed on the end of the lever 244. Whenfully retracted, the cam 158 is in driving or forward feeding engagementwith the internal cam plate wall, but upon motor reversal as has beenstated, the earn 158 acting upon an internal wall 256 of the plate 162quickly displaces the projection 248 outwardly consequently depressingthe striker to switch-opening position. it will be apparent from FIG. 14that the switch 25%} is permitted to assume its normally closed positionduring machine operation by a spring 1258 connecting the lever 244 tothe bracket 246, the spring serving to urge the striker 242 intoposition to be engaged by the projection 2% upon motor reversal.

Work Controls Adjwnctz've to Guidance System As shown in FIG. 1 thecontrol box 1'22 (FIGS. 1, l7 and 19) in which the bias supply control126 is mounted also includes a manual stop switch 262 and a rotaryselector switch 264. The latter is advantageously empioyed to select anypreferred one of four modes of operation of the machine next to beexplained according to whether this switch is turned to its position 1,2 or 3 indicated on the box 122. in switch position 1, used for normaloperation, the machine drive and work guidance is controlled solely bythe foot switch 124 as deseribed. The second mode is foilowed when it isdesired to have operation of the machine automatically stop at the endof each work piece, i.e. at the finish the throat plate 39 immediatelyahead of the guidance cell Hi8 and preferably disposed parallel to theoperating path of the feed dog 4i). Referring to P16. 19, in practicingthis automaticwork kick out, a switch S2 now being closed, a switch S3being open, and a switch S4 being closed at position B, the foot switch124 is held depressed to cause the machine to operate as previouslydescribed, the motor 42 continuing to run by virtue of energization of arelay K3 and consequent closure of a contact K3A1 which parallels thefoot switch. When the seam being inserted has been guided past someselected corner, for instance the next to last one, the operator willrelease the foot switch 124, and a voltage is thereby applied to atransistor amplifier 268 and to a coil K4, the machine continuing tofunction under the automatic work guidance system. Now, by action of thecell 255, upon bein uncovered by the work at its next, i.e. last,corner, an added voltage surge is applied to the relay K4 via thetransistor amplifier 268, and the relay K4 then opens a contact K4B1(FIG. 19) to deenergize the relay K3 thereby removing the motor drivevoltage to stop the machine with its needle in up position. it will beappreciated that this second mode of operation provides added freedomfor an operator; he may, during the final stage of automatic guidance'onone work piece, as soon as he has released the foot switch, reach forthe next piece to be processed for instance, being assured that themachine will automatically cease operation at the correct point, forexample at the locality where the seam was initially started.

In a third mode of operation now to be explained and termed the kick offfunction, the selector switch 264 is also at position 3. This mode isused in connection with peripheral operations when it is desirable toterminate operation of the machine at any point along the operating pathother than at a corner. When the point is reached a manual kick olfswitch 272 (FIGS. 1 and 19) is actuated. This results in a signal beingtransmitted via the closed contact B of the switch S4 to a linedesignated D and hence to the power amplifier 114 causing the servomotor forthwith to steer the work away from the operating zone. This isto say that the resultant overriding command tothe servo motor requiresthe wheel 3b to rotate to turn the work rapidly clockwise (as viewedfrom above) about its own centroid. The machine consequently stops whenit has thus caused the work to render the cell 266 exposed to light fromthe bulb 116.

A fourth mode of operation is advantageous in speeding up output,particularly when smaller work pieces are being processed, and is termedthe kick through arrangement. For this purpose the selector switch 264is adjusted to position 2 (FIG. 1) causing the switches S2; S3 (FlG. 19)to be closed, and a contact A of the switch S4 to be closed while itscontact B is open. in this mode the main motor 42 is permitted to runcontinuously as the work pieces are successively guided and sewn, onedirectly following completed guidance of another. relays K1, K2, K3 andK5 are energized by actuating the switch 124 and the motor 42 drives byvirtue of the closure of the contact KBAI. Prior to reaching the feedout corner the switch 124 is released to energize the coil K4 and thetransistor amplifier 268. As the kick out cell 266 senses the end ofeach work piece (in the manner described for the second mode), the cellapplies a surge through the transistor amplifier 268 further to energizethe coil Kd and close a contact K t-A2. As a result power is now fedfrom an independently powered circuit including a potentiometer 274(FIG. 19), via the contact lid-A2 and the line D, to the power amplifier114 instead of an input from the preamplifier M2, the velocity of thewheel thus being modified to permit the feed dog it to operate forthwithto feed the work in a substantially straight line away from theoperating zone. Now, when the operator presents the next work piecethereby again covering the cell 266, the contact KdAZ opens and thecontact K4-B2 closes to transmit the normal guidance error signal fromthe preamplifier 112. To stop the drive motor 42 the switch 262 must beactuated when the series of work pieces has been processed.

FIG. 26 illustrates an alternate type of steering presser in the form ofa bowed or U-shaped spring 2% which may be substituted for the steeringpresser roll 82 in frictionally exerting, cooperatively with thesteering wheel 86, suitable steering torque on the work. The spring assis secured at its ends to a horizontal bracket 282 fast on the head 38,lies in a vertical plate, and has a mid portion 234 movable heightwisein yieldaole work engaging position. The width of the spring portion 284is preferably at least as great as that of the toothed perirneter of thewheel 86 and, notably, is yieldable in trans F lation parallel to thedirection of feeding. If desired, of

a,oso,ese

11 course, opposed margins of the portion 284 may be rounded upwardlyfrom the work. For automatically guiding work having certain physicalcharacteristics or combinations thereof (hardness, roughness,resiliency, variable thickness, flexibility, etc.), it is believed thespring 80 will assist in overcoming adverse influence on steering due towork distortion or slippage. As shown in FIG. 20, to facilitatepresentation and removal of the work, the portion 284 is mounted to bemovable heightwise together with the feed presser roll 44 by the post52. Thus, a yoke 286 attached to the portion 284 is connected by a coilspring 288 to one end of a lever 29%, the other end of which ispivotally secured by a screw 292 to a block 294 clamped on the post 52.Means including a vertical set screw 296, a pivotal lever 298, and aneccentric cam 30% manually adjustable by a control knob 302 are providedfor obtaining differential in operating pressure between the feedpresser roll 44 and the spring 28%.

Machine Operation It will be understood that the machine is providedwith a supply of thread T (KG. 1) for the line of sewing to be insertedby the needle 26 as determined by the automatic work guidance mechanismabove described. Also, it will be understood the usual shuttle mechanism(not shown) is mounted in the post 32 and operated from a drive belt 394on a pulley 306 (FIG. 9) secured on the main shaft.

By use of the knob 236 the operator will first have selected the motorspeed with which the seam is to be inserted. Having connected themachine and controls to their respective power sources an operatorplaces the upper to be sewn on the machine post 32, lowers the presserfoot post 52 by means of the lever 60, and, while ascertaining that theend portion of the strip S is extending suitably from the exit of theguideway 70, holds the extremity of the thread T for the first stitch ashe actuates the treadle 124. Without further attenion the sewing machinethen continues to operate, alternating steps of translatory work feedingand automatic steering, the latter being dictated by the curvature ofthe work edge, until the work piece has traversed the desired course andis automatically ejected. The resultant seam securing the upper andstrip in parallel edge relation will extend parallel to the edge thecurvature of which is being sensed by the cell 138. Feeding in straightline translation is effected by the dog 40 in approximately half themachine cycle, the other half being used at least in part for steer ingby means or" the wheel 80. In the steering intervals, which normallyoccur only when the needle has engaged the work to serve as a turningcenter therefor, the wheel 80 is caused by the servo motor 84 to rotatewith a torque frictionally applied to the work. A servo motor couldconceivably be electrically controlled so that its output would besynchronized in a cycle with the work engaging phase of the needle, butsince this appears to necessitate theme of unduly expensive equipment,this invention provides for the servo motor 84 continuously to receivesteering signals, but at practically no added cost effectively couplesthe output of the servo motor to the work via the wheel 89 only whilethe needle is engage This is accomplished by making use of theheightwise movement of the feed dog 40 to control alternation of feedingand steering. Thus, when the feed dog moves up to feed, it acts to liftthe work off the steering wheel 8%, or (if the work be less stiff) actsthrough the post 52 to reduce the pressure with which the work isengaged at its steering locality by the wheel St so that the latter thenrotates harmlessly and is temporarily ineffective. On descent the dogreturns the work to be coupled to the wheel 80 for steering about thenow engaged needle.

During the automatic guidance of the work with respect to the needle,the curvature sensing cell 1% continuously responds electrically to thedegree of light incident from the source its not intercepted by the work12 and thus produces a signal, which varies from the DC. referencevoltage from the bias supply 110, which corresponds with deviation ofthe controlling curvature, in this case the work edge, from its correctposition. Accordingly, a signal in terms of DC. voltage is derived to beconverted to an AC. signal which, when amplified and damped asexplained, is fed to the servo motor S4. The latter therefore reversiblyand continuously drives the steering wheel 36 in the proper directionand with correct speed potentially to apply a moment to the work U torestore it to its correct or zero error position after each increment offeed in translation effected by the dog 40.

Considered analytically, operation of the machine will vary according tothe requirements of particular work, it being helpful in some cases toprovide the steering presser roll 82 and/ or the wheel 8% with aperiphery of a rubberlike, friction-enhancing material. In theillustrative machine a short interval may occur in the cycle in which itis possible that, although the needle 26 is still descending or has justdescended into the work, the wheel 86 may be exerting a low torque butbe ineffective to steer the work by reason of the fact that the dog 40is still engaging the work with sufiicient clamping pressure to causethe wheel 89 simply to slip. It should be noted, however, that thepreferred timing and organization is not such that work clampingpressure of the feed means, i.e. the dog 40 and the roll 4-4, is capableof exerting torque to steer the work either about the needle or the workengaging locality of the Wheel 80. In other words, as indicated in FIG.8, the feeding and steering portions of a cycle are normally exclusive,steering occurring only when the necdle engages the work, and feedingoccurring only when the needle is disengaged or at least causes noappreciable drag. Slight exception may occur in some machines when thereadvantageously is a very brief overlapping of the feeding and steeringfunctions by reason of a small work engaging pressure being allowed tobe exerted during steering time by the feed presser, for instance wherefeeding is phase dispaced from needle motion. The feed presser is thenproviding a light drag or pivot to enable the needle to pierce the workjust before the feed stroke is com- .plete; in this situation the needleis still out of the work when steering action commences.

In conjunction with the automatic work guidance means provided, theseveral control features above explained have been found particularlyhelpful, both individually and collectively, to the operator. Thus, by lcans of the device 156 the needle 26 never interferes with properloading or removal of the work from the machine, the mechanism depictedin H6. 14 operating as explained, reliably to lift the needle from thework almost instantly when the treadle 124 is released to stop themachine. Also, during continuous operation of the machine on the workbeing automatically guided, it is found advantageous to employ thestitch-length changing mechanism at a selected portion of the operatingpath. As explained with reference to the FIGS. 9-11, the operator onlyneeds to actuate the knee pad 174 as the selected portion (the sharpinside curvature of FIG. 13, for instance) approaches the operating zoneof the needle, to shift the shaft 154 axially to the right (in FIG. 9)and thus shorten stitch length. This makes for a stronger seam in acritical area and produces a more uniformly stitched article.

Selection of one of the three settings 1, 2, or 3 for the selectorswitch 264- enables the operator to have the work automatically guidedin the machine to the selected ejection or stop position. As aboveexplained, the resultant circuitry causes kick-out, kick-through, orkickoff. In the kick-out mode, the switch 264 being in position 3, theoperator simply releases the switch 124 as the work is being guided tocause the next or final corner to approach the ejection control cell266. Upon this corner uncovering the cell 266, it causes the drive motorvoltage to be cut off and the machine to stop in needle 13 up position,the work being ejected if it was the last corner traversing the cell266. Normally, of course, the switch 124 may be released at any timesimply to stop operation of the machine.

In the kick-through mode, the switch 264 being at position 2, when thefoot switch 124 is released the machine continues its normalautomatically guided sewing until the next (normally last) work corneradvances and sufficiently uncovers the cell 266, whereupon the dog 40feeds the work straight from the needle to permit the next piece of workto be presented thereto without interrupting operation of the machine.The kick-01f mode permits immediate feed-out of the work upon manualoperation of the switch 272. It will be understood that the thread T andstrip S will be severed as convenient to provide the individual,assembled work pieces.

Having thus described our invention, what we claim as new and desire tosecure by Letters Patent of the United States is:

I. In a machine having a tool for operating on a work piece, mechanismintermittently operative to feed the work piece an increment intranslation past the tool, and

edge curvature controlled means adapted to initiate and exert a steeringtorque on the work piece and about the operating locality of the tooleach time the feeding mech anism has operated to determine the operatingpath of the tool on the work piece.

2. 'In a machine having a work support, a relatively movable tool foropera-ting on successive portions of a. Work piece on the support, meansfor feeding the work intermittently in translation with respect to thetool, a work sensing circuit, and automatic guidance means continuouslyresponsive to said circuit and frictionally operable in time relation tothe work feeding means for controlling steering movement of the workpiece with respect to the tool.

3. In a machine having a work support provided with an operating zoneand on which a work piece is intermittently advanced in translation onestep beyond said zone, a relatively movable tool cooperative therewithat the operating zone by engagement with successive portions of a workpiece, automatic guidance mechanism including a member frictionallyengageable with the work piece at only a single locality spaced from thetool for steering the Work piece with respect thereto, and means forcausing said guidance mechanism effectively to operate when the tool isoperative in said zone.

4. In a machine having a tool for operating on successive portions of awork piece, a work support on which the work piece is to be guided withrespect to the tool by operation of work feeding means and work steeringmeans, said feeding means including a member having components ofmovement both heightwise and in translation, curvature sensing means forcontrolling said work steering means, and mechanism responsive to one ofthe components of motion of said member for effectively operating thesteering means alternately with the feeding means.

5. ins machine having a tool for operating on or near the margin of aWork piece and means for feeding the work piece step-by-step past thetool, mechanism engageable with the work piece at one locality only forsteering the work with respect to the tool according to the curvature ofthe work edge in the operating locality of the tool, and means foreffectively operating said steering mechanism alternately with saidfeeding means.

6; A machine comprising a tool for operating on the margin of a Workpiece, means operable inwardly of the work piece from the tool forfeeding the work piece stepby-step past the tool, mechanism including asteering member and cooperative presser member operative at only asingle locality farther inwardly of the work piece from the feedingmeans for steering the work piece with work edge immediately ahead ofthe tool, and means for 1a effectively operating said steering mechanismwhen said feeding means is inoperative.

7. In a machine comprising a tool adapted to engage successive marginalportions of a work piece and having means for advancing the work piecepast the tool each time the tool is retracted therefrom, work steeringmeans including a steering member and a presser member cooperativelyengageable with opposite sides of the work piece inwardly of its margin,means for controlling the steering member according to marginalcurvature of the work in a locality just ahead of the tool, andmechanism responsive to operation of the work advancing means forcontrolling relative movement of the steering and presser members intoand out of cooperative work-em gaging positions whereby the worksteering means is effective bodily to turn the work about the tool onlywhen the tool is in engagement therewith.

8. In a machine comprising a tool engageable with the margin of a workpiece and having means for intermittently advancing the work piece pastthe tool, work steering means engageable with opposite sides of the workpiece at only a single locality inwardly of its margin, said steeringmeans being continuously responsive to the curvature of the margin inits portion immediately ahead of the tool, and mechanism for renderingsaid steering means effective in each interval that the work piece isnot being advanced, reversibly to swing the work piece about a turningcenter substantially at the zone of engagement of the tool therewith.

9. In a machine having a reciprocable tool for operating on a work pieceand comprising work feeding means including a first presser member forfeeding the work past the tool, automatic work steering means includinga second presser mem er spaced from the first, and control meansoperative in time relation to the operation of the tool for alternatelyshifting the presser members into and out of efiective engagement withthe work whereby the work is alternately fed and steered.

10. In a sewing machine having a reciprocable needle and a throat plateformed with a hole for receiving the same, an orbitally actuated dog forfeeding the work past the needle istep-by-step, and automatic worksteering means including only one pair of work-engaging members forbodily turning the work about the needle when the latter has penetratedthe work.

11. A machine as set forth in claim 10 further characterized in thatelectrical means is provided for con trolling the velocity of one ofsaid members in accordance with change in curvature.

12. A machine as set forth in claim 11 and further characterized in thatthe electrical means includes a circuit comprising a light responsivedevice arranged in the throat plate ahead of the needle by a spacing inthe range of substantially from zero to five feeding steps, and said onemember is a wheel reversibly rotatable according to the curvature of anedge of the work.

:13. In a machine having a reciprocable tool for operat' ing onsuccessive portions of a work piece, a work support over which the workpiece is to be fed and guided with respect to the tool to cause its pathof operation to extend in parallel relation to the edge of the workpiece, a feed member movable heightwise of the work support forintermittent engagement with one side of the work piece to feed it intranslation when the tool is retracted, a presser arranged to cooperatewith said feed member by engagement with the work piece on its oppositeside,

mounting means for said presser yieldingly to effect its.

work engagement during tool retraction, and work guidance mechanismcomprising a continuously operative steering wheel and cooperativesteering presser arranged, respectively, to engage the work pieceinwardly of the feed member, the velocity of said wheel being controlledby sensing means responsive to change in curvature of said edge in thevicinity of the tool, and the steering presser having operativeconnection to said mounting means acsaeee whereby the guidance mechanismis effective to pivot the work piece about the tool only when it engagesthe Work piece.

14. A machine having a reciprocable tool for operating on successiveincrements of sheet material, comprising mechanism operable to advancethe sheet material rectilincarly an increment between successiveengagements of the tool with the material, guidance mechanism operablefor exerting torque on the material at only a single locality spacedfrom said engagements of the tool, curvature monitoring means forcontrolling the potential torque to be exerted by the guidancemechanism, and means for causing said torque actually to be imparted bythe guidance mechanism to the sheet material only when the latter isbeing engaged by the tool.

15 in a machine having a tool for operating on successive portions of awork piece, means for feeding the work piece rectilinearly an incrementbetween the succersive operations of the tool, and guidance mechanismoperative simultaneously with the tool bodily to turn the work pieceabout the operating zone of the tool when the latter is in engagementwith the work piece, said mechanism including a servomotor continuouslyresponsive to signals generated from a controlling pattern.

16. A machine as set forth in claim 15 and further characterized in thatthe guidance mechanism comprises only one member reversibly driven withvariable velocity in frictional engagement with the work piece, thevelocity of the member corresponding with the concurrent deviation ofthe curvature of said pattern from the preceding rectilinear feedingincrement whereby torque exerted by the member on the work piece seeksto reduce such deviation to zero.

17. In a sewing machine having a reeiprocable needle, 2. throat platehaving a needle receiving hole over which work to be sewn is to beguided, means including a member movable heightwise of the throat platefor feeding the work an increment in translation each time the needle isretracted therefrom, work steering means including a wheel andcooperative presser engageable with the work under variable pressure ata single locality spaced from the operating path of the needle and closeto the work supporting surface of the throat plate, a curvature sensingcircuit including a light sensitive device embedded in said platesurface immediately ahead of the needle hole for controlling thevelocity of the wheel, and mechanism responsive to the heightwise motionof said feeding member for causing the wheel and the presser to engagethe work with greater pressure while the needle is available to serve asa pivot therefor.

18. A sewing machine as set forth in claim 17 and further characterizedin that said circuit includes a biased power supply for determining anull line along which zero steering error occurs, and means for shiftingthe null line transversely of the direction of feeding.

19. In a machine of the type having a work support, a tool movabletoward and from an operating zone on the support to engage successiveportions of a work piece thereon, and means movable relatively to thesupport to advance the work piece in translation past the tool while itis inoperative thereon, the combination comprising guidance mechanismfor exerting variable torque on the work piece at a single localityclose to the surface of said support, said mechanism comprising aservo-controlled steering wheel the work-engaging perimeter of which isdisposed adjacent to said surface and a presser cooperative with saidperimeter, means for actuating the presser toward the perimeter withgreater pressure while the tool engages the work piece, said actuatingmeans comprising a yieldingly pivotal lever for carrying said presserand having operative connection to said work advancing means, acurvature sensing circuit for continuously controlling the velocity ofthe steering wheel, said sensing circuit including a light sensitivedevice disposed closely adjacent to the operating zone and transverselyof a null lb line, and a source of light disposed in the vicinity ofsaid Zone and on the opposite side of the work piece from said device.

20. In a machine having a tool for operating on successive portions ofsheet material of irregular curvature, mecharnsm for feeding thematerial in increments past the tool, work guidance mechanism includinga light sensitive cell responsive to curvature of the material in alocality just ahead of the operating zone of the tool, a tubular mainshaft for driving the tool, operating connections including eccentricmeans on the shaft and by which said feeding mechanism is driven, acollar rotatable with the main shaft and providing a pivot for saideccentric means, and a rod shiftable axially within the main shaftduring operation of the machine to change the eccentricity of saideccentric means to modify the length of the feeding increments uponsharp change in said curvature approaching the cell.

21. In a sewing machine having stitch forming devices and means forfeeding a work piece in translation intermittently past these devices, apartly tubular main shaft having operative connections, respectively,for driving said means and devices to insert a seam of normal stitchlength, automatic guidance means responsive to edge curvature of thework piece in a locality immediately ahead of the devices forcontrolling steering of the work with respect thereto, said operativeconnections to the work feeding means including a strap cccentricallyreceiving the tubular portion of the main shaft, mechanism shiftableaxially of the latter to modify the eccentricity of the strap, andcontrol means operable as sharper edge curvature approaches the devicefor thus shifting the mechanism to change the stitch length from normalduring negotiation of the sharper curvature and then back to normalwithout interrupting operation of the machine.

22. In a machine having a tool for operating on a flat work piece ofirregular edge curvature, mechanism for feeding the work piece intranslation with respect to the tool, electrical means including a lightsensitive device responsive to rays directed past the work piece forsteering the latter according to its curvature and in time relation tosaid feeding mechanism, and control means including a second lightsensitive device located immediately ahead of the first-mentioned devicefor causing the steering means at a selected corner of the work topermit the feeding mechanism to move the work piece in a straightdirection away from the tool.

23. In a machine having a tool adapted to operate along the margin ofsheet material, means for feeding the material in translatory incrementspast the tool, mechnism for applying a steering torque at a singlelocality to guide the material with respect to the tool according to thecurvature of said margin, and a control circuit including a lightsensitive device arranged ahead of the tool and energizable upon beingincreasingly uncovered by a portion of the margin automatically to stopoperation of the machine.

24. In a machine having a tool adapted to operate along the margin ofsheet material, means for feeding the material in translatory incrementspast the tool, mechanism for applying a steering torque at a singlelocality to guide the material with respect to the tool according to thecurvature of said margin, said mechanism including a curvature sensingcircuit comprising a servomotor, a power amplifier connected to themotor, and a preamplifier from which sensing signals are normallytransmitted to the power amplifier, and a control circuit energizable atthe will of the operator to send an overriding command to the poweramplifier whereby the scrvomotor abruptly causes the guidance mechanismto apply a torque for ejecting the material from the operating localityof the tool.

25. In a machine having a tool adapted to operate along the margin ofsheet material, means for feeding the material in translatory incrementspast the tool,

mechanism for applying a steering torque at a single locality to guidethe material with respect to the tool according to the curvature of saidmargin, said mechanism including a curvature sensing circuit comprisinga servomotor, a power amplifier connected to the motor, and apreamplifier from which sensing signals are Y normally transmitted tothe power amplifier, a control circuit including a light sensitivedevice disposed ahead of the tool and energizable upon beingincreasingly uncovered by a portion of the margin, and a second controlcircuit normally disconnected from the power amplifier and having anindependent input, the arrangement being such that when said device isthus energized said second control circuit provides an input to thepower amplifier in lieu of that from the preamplifier whereby saidfeeding means is permitted to feed the material in a substantiallystraight line away from the tool.

26. In a machine having a tool arranged to operate on or near the edgeof a work piece, means for feeding the work piece rectilinearly anincrement between successive operations of the tool, guidance mechanismincluding a wheel frictionally engageable with the work piece at alocality spaced from the operating path of the tool, mechanism foroperating the guidance mechanism effectively only when the tool is inengagement with the work piece to serve as a center for its turningmovement, and an electric curvature sensing means including a lightresponsive device for controlling the velocity of said wheel, and aservo motor-tachometer responsive to said device for continuouslydriving the wheel, said sensing means being adapted to detect change incurvature of said edge, and said device being spaced immediately aheadof the tool and close to the edge for supplying controlling power tosaid motor whereby the wheel velocity is continuously corrected inaccordance with said curvature change.

References Cited in the file of this patent UNITED STATES PATENTS

1. IN A MACHINE HAVING A TOOL FOR OPERATING ON A WORK PIECE, MECHANISMINTERMITTENTLY OPERATIVE TO FEED THE WORK PIECE AN INCREMENT INTRANSLATION PAST THE TOOL, AND EDGE CURVATURE CONTROLLED MEANS ADAPTEDTO INITIATE AND EXERT A STEERING TORQUE ON THE WORK PIECE AND ABOUT THEOPERATING LOCALITY OF THE TOOL EACH TIME THE FEEDING MECHANISM HASOPERATED TO DETERMINE THE OPERATING PATH OF THE TOOL ON THE WORK PIECE.